1. Field of the Invention
The present invention relates generally to coaxial cable connectors. More particularly, the present invention relates to coaxial F-connectors adapted to insure the establishment of a proper ground during installation. Known prior art is classified in United States Patent Class 439, Subclasses 241, 247, 322, 548, 553, 554, 585, and 587.
2. Description of the Related Art
Popular cable television systems and satellite television receiving systems depend upon coaxial cable for distributing signals. As is known in the satellite TV arts, coaxial cable in such installations is terminated by F-connectors that threadably establish the necessary signal wiring connections. The F-connector forms a “male” connection portion that fits to a variety of receptacles, forming the “female” portion of the connection.
F-connectors include a tubular post designed to slide over coaxial cable dielectric material and under the outer conductor at the prepared end of the coaxial cable. The exposed, conductive sheath is usually folded back over the cable jacket. The cable jacket and folded-back outer conductor extend generally around the outside of the tubular post and are typically coaxially received within the tubular connector. A continuity contact between the sheath and the body of the connector is needed. Moreover, contact must be made with the threaded head or nut of the connector that should contact the female socket to which the connection is made.
F-connectors have numerous advantages over other known fittings, such as RCA, BNC, and PL-259 connectors, in that no soldering is needed for installation, and costs are reduced as parts are minimized. For example, with an F-connector, the center conductor of a properly prepared coaxial cable fitted to it forms the “male” portion of the receptacle connection, and no separate part is needed. A wide variety of F-connectors are known in the art, including the popular compression type connector that aids in rapid assembly and installation. Hundreds of such connectors are seen in U.S. Patent Class 439, particularly Subclass 548.
However, the extremely high bandwidths and frequencies distributed in conjunction with modern satellite installations necessitate a variety of strict quality control factors. For example, the electrical connection established by the F-connector must not add electrical resistance to the circuit. It must exhibit a proper surge impedance to maintain a wide bandwidth, in the order of several Gigahertz. Numerous physical design requirements exist as well. For example, connectors must maintain a proper seal against the environment, and they must function over long time periods through extreme weather and temperature conditions. Requirements exist governing frictional insertion and disconnection or withdrawal forces as well.
Importantly, since a variety of coaxial cable diameters exist, it is imperative that satisfactory F-connectors function with differently sized cables, such as RG-6 and RG-59 coaxial cables that are most popular in the satellite television art.
It is important to establish an effective electrical connection between the F-connector, the internal coaxial cable, and the terminal socket. One facet of the problem involves electrical continuity that must be established between the connector nut and the usually-barbed post within the connector. More particularly, it is important to establish a dependable electrical connection between the front nut, the internal post, the post shank, and the coaxial cable sheath.
Proper installation techniques require adequate torquing of the connector head. In other words, it is desired that the installer appropriately tighten the connector during installation. A dependable electrical grounding path must be established through the connector body to the grounded shield or jacket of the coaxial cable. Threaded F-connector nuts should be installed with a wrench to establish reasonable torque settings. Critical tightening of the F-connector nut to the threaded female socket or fixture applies enough pressure between internal parts and the inner conductor of the coaxial cable to establish proper electrical connections. When fully tightened, the head of the tubular post of the connector directly engages the edge of the outer conductor of the appliance port, thereby making a direct electrical ground connection between the outer conductor of the appliance port and the tubular post; in turn, the tubular post is engaged with the outer conductor of the coaxial cable.
Many connector installations, however, are not properly completed. It is a simple fact in the satellite and cable television industries that many F-connectors are not appropriately tightened by the installer. A common installation technique is to torque the F-connector with a small wrench. In some cases installers only partially tighten the F-connector. Some installations are only hand-tightened. As a consequence, proper electrical continuity may not be achieved. Such F-connectors will not be properly “grounded,” and the electrical grounding path can be compromised and intermittent. An appropriate low resistance, low loss connection to the female target socket, and the equipment connected to it, will not be established. Unless a proper ground path is established, poor signal quality, and RFI leakage, will result. This translates to signal loss or degradation to the customer.
U.S. Pat. No. 3,678,445 issued Jul. 18, 1972 discloses a shield for eliminating electromagnetic interference in an electrical connector. A conductive shielding member having a spring portion snaps into a groove for removably securing the shield. A second spring portion is yieldable to provide electrical contact between the first shell member and a second movable shell member.
U.S. Pat. No. 3,835,442 issued Sep. 10, 1974 discloses an electromagnetic interference shield for an electrical connector comprising a helically coiled conductive spring interposed between mating halves of the connector. The coiled spring has convolutions slanted at an oblique angle to the center axis of the connector. Mating of the connector members axially flattens the spring to form an almost continuous metal shield between the connector members.
U.S. Pat. No. 3,739,076 issued Jun. 12, 1973 discloses a coaxial connector with an internal, electrically conductive coil spring mounted between adjacent portions of the connector. As an end member is rotatably threaded toward the housing, an inwardly directed annular bevel engages the spring and moves it inwardly toward an electrically shielded portion of the cable. The spring is compressed circumferentially so that its inner periphery makes electrical grounding contact with the shielded portion of the cable.
U.S. Pat. No. 5,066,248 issued Nov. 19, 1991 discloses a coaxial cable connector comprising a housing sleeve, a connector body, a locking ring, and a center post. A stepped, annular collar on the connector body ensures metal-to-metal contact and grounding.
U.S. Pat. No. 4,106,839 issued Aug. 15, 1978 shows a coaxial connector with a resilient, annular insert between abutting connector pieces for grounding adjacent parts. A band having a cylindrical surface is seated against an internal surface. Folded, resilient projections connected with the band are biased into contact. The shield has tabs for mounting, and a plurality of folded integral, resilient projections for establishing a ground.
U.S. Pat. No. 4,423,919 issued Jan. 3, 1984 discloses a connector having a cylindrical shell with a radial flange, a longitudinal key, and a shielding ring fitted over the shell adjacent the flange. The shielding ring comprises a detent having end faces configured to abut connector portions when the detent fits within the keyway, whereby the shell is prevented from rotating.
U.S. Pat. No. 4,330,166 issued May 18, 1982 discloses an electrical connector substantially shielded against EMP and EMI energy with an internal, conductive spring washer seated in the plug portion of the connector. A wave washer made from beryllium copper alloy is preferred.
U.S. Pat. No. 6,406,330 issued Jun. 18, 2002 employs an internal, beryllium copper clip ring for grounding. The clip ring forms a ground circuit between a male member and a female member of the electrical connector. The clip ring includes an annular body having an inner wall and an outer wall comprising a plurality of circumferentially spaced slots.
U.S. Pat. No. 7,114,990 issued Oct. 3, 2006 discloses a coaxial cable connector with an internal grounding clip establishing a grounding path between an internal tubular post and the connector. The grounding clip comprises a C-shaped metal clip with an arcuate curvature that is non-circular. U.S. Pat. No. 7,479,035 issued Jan. 20, 2009 shows a similar F-connector grounding arrangement.
U.S. Pat. No. 7,753,705 issued Jul. 13, 2010 discloses an RF seal for coaxial connectors. The seal comprises a flexible brim, a transition band, and a tubular insert with an insert chamber defined within the seal. In a first embodiment the flexible brim is angled away from the insert chamber, and in a second embodiment the flexible brim is angled inwardly toward the insert chamber. A flange end of the seal makes compliant contact between the port and connector faces when the nut of a connector is partially tightened, and becomes sandwiched firmly between the ground surfaces when the nut is properly tightened. U.S. Pat. No. 7,892,024 issued Feb. 22, 2011 shows a similar grounding insert for F-connectors.
U.S. Pat. No. 7,824,216 issued Nov. 2, 2010 discloses a coaxial connector comprising a body, a post including a flange with a tapered surface, a nut having an internal lip with a tapered surface which oppositely corresponds to the tapered surface of the post when assembled, and a conductive O-ring between the post and the nut for continuity. Similar U.S. Pat. No. 7,845,976 issued Dec. 7, 2010 and U.S. Pat. No. 7,892,005 issued Feb. 22, 2011 use conductive, internal O-rings for both grounding and sealing.
U.S. Pat. No. 6,332,815 issued Dec. 25, 2001 and U.S. Pat. No. 6,406,330 issued Jun. 18, 2002 utilize clip rings made of resilient, conductive material such as beryllium copper for grounding. The clip ring forms a ground between a male member and a female member of the connector.
U.S. Pat. No. 6,716,062 issued Apr. 6, 2004 discloses a coaxial cable F connector with an internal coiled spring that establishes continuity. The spring biases the nut toward a rest position wherein not more than three revolutions of the nut are necessary to bring the post of the connector into contact.
U.S. Pat. No. 7,841,896 issued Nov. 30, 2010, and entitled “Sealed compression type coaxial cable F-connectors”, which is owned by the instant assignee, discloses axially compressible, high bandwidth F-connectors for interconnection with coaxial cable. An internal, dual segment sealing Plunger activated by compression provides a seal. Each connector nut interacts with a tubular body and a rigid, conductive post coaxially extending through the connector. A post barbed end penetrates the cable within the connector. A metallic end cap is slidably fitted to the body. A tactile system comprising external convex projections on the body complemented by a resilient, external O-ring on the end cap aids installers who can properly position connectors with the sense of touch.
For an adequate design, structural improvements to compressible F-connectors for improving continuity or grounding must function reliably without degrading other important connector requirements. Compressible connectors must adequately compress during installation without excessive force. An environmental seal must be established to keep out water. The coaxial cable inserted into the connector must not be mechanically broken or short circuited during installation. Field installers and technicians must be satisfied with the ease of installation. Finally, the bottom line is that a reliable installation must result for customer satisfaction.
As implied from the above-discussed art, many prior art attempts at enhanced grounding exist. Several solutions involve the addition of a conductive grounding member within the fitting that physically and electrically bears against critical parts to enhance continuity. Some forms of grounding involve radially positioned or circuit elements that contribute to an electrical grounding path. Recently, it has become apparent to us that known radial grounding designs directed at the above-discussed continuity problem may not, under certain conditions, adequately insure and establish electrical contact. We have found that, where used, the radial grounding insert must be captivated and peripherally, radially pressured to promote grounding. Further, as recent efforts to insure grounding center upon nut-to-post contact, the radial grounding must be established between the nut and post.